Organic electroluminescent elements have attracted attention as a next-generation illumination light source because they enable planar light-emission and enable light emission of any color tone depending on the selection of light-emitting substances, and have been vigorously developed with the aim of practical use. In particular, research and development has been actively conducted especially with regard to technologies for extending the lifetime, methods for extending the lifetime by various design and technological developments of devices have been proposed. However, problems remain in order to realize sufficient improvement in a lifetime property in comparison with conventional main lighting, that is, fluorescent lamps.
JP 2006-172763A (Patent Literature 1) discloses a method for improving all of whiteness, luminance efficacy, and a lifetime. In this method, a non-luminescent interfacial layer is interposed between a light-emitting layer containing a fluorescent dopant and a light-emitting layer containing a phosphorescent dopant, and a fluorescent light-emitting layer is positioned closer to a cathode than a phosphorescent light-emitting layer is, and a red phosphorescent light-emitting layer is formed into a thin film having an island shape. However, Patent Literature 1 does not describe change in chromaticity and does not disclose clearly technologies for improving the lifetime of a multiunit element in which change in chromaticity tends to increase with the passage of time.